ASME IX PQR using STT

Date 08-21-2009 02:37

I would consider STT to be "controlled" short circuiting arc, since the electrode does contact the puddle according to Lincoln's description of the process. As long as you treat it as short-circuiting transfer mode under the current rules, there should be no problem. If you try to call it GMAW-P, there may be some issues raised. Perhaps one day there will be specific rules for waveform controlled welding.

http://www.lincolnelectric.com/knowledge/articles/content/future1.asp

By Lawrence (*****)

Date 08-21-2009 04:21 Edited 08-21-2009 04:25

Welcome to the forum JM!

I would list a number of things here because STT is not only a form of GMAW-S (short circuiting transfer mode) it is also a hybred power process CC/CV with several dozen synergically (adaptive feedback) parameters.

1. Power supply type ie Powerwave 355 etc.
2. Specific STT program on that software package
3. Trim setting
4. Wire feed speed

Actual voltage and Current are pretty much impossible to determine (accuratly) from reading the run time digital readouts. The current is only a rough almagated average and the votage is not displayed at all.. Trim numbers are not related to real time working voltage.

Without listing these things you can't really generate WPS that will be repeatable and compliant with the PQR.

In my opinion It would be impossible to be compliant and with code and run Traditional GMAW-S production within the scope of a GMAW-STT PQR, just as it would be impossible to run GMAW-S in production with an STT PQR..... Even though both are considered the same basic process (GMAW-S _& STT) It is just not possible to calculate current and voltage from one process to the other.

By JM_VRCIC (*)

Date 02-09-2010 16:54

Hi Lawrence, many thanks for your detailed answer. Now, I wonder after reading your answer under what code should I qualify a WPS that is going to be use in a pipe workshop (I don't know how you call it there) where we weld pipes and fitting (spools) to be erected in field? Because I know what will be the answer here, our manager will say, I need a WPS anyway so qualify it. Can you give some tips?

By Lawrence (*****)

Date 02-09-2010 17:50

Juan,

I'm not qualified to offer an opinion on this one.

But if you say a little more about your work, telling us about the intended service environment for the pipes you are welding, I think you will get some excellent advice.

ASME and AWS have some pretty big differences as far as PQR's go. So you are wise to be sure your on the right track here :)

By JM_VRCIC (*)

Date 02-10-2010 12:34

Thanks Lawrence. In our workshop we used to weld pipes according to ASME B31.3, some supports according to AWS D1.1 and sometimes, but not so often, some API 1104 spools. Well, hope this is useful in order to receive someone advice/info about qualifying a PQR by ASME or any other code.

By 803056

Date 02-10-2010 21:15

You can qualify the procedure per ASME Section IX without recording the welding parameters because they are considered to be nonessential variables by ASME.

When you develop the WPS use the parameters you do know such as wire feed speed, travel speed, etc. If you are using a "canned" computer program, list the appropriate program number and the model number (not serial number) of the welding machine to be used.

I tend to agree with Lawrence on the issue of developing a WPS the welder can use, but we are talking about ASME Section IX. It is entirely possible to write a WPS the is of little use to the welder, but fulfills the requirements of Section IX.

ASME Section IX and reality from the welder's vantage point have little in common.

Best regards - Al

By JM_VRCIC (*)

Date 02-11-2010 15:53

Awesome answer...

Never the less, I have already sent to the ASME board to answer and maybe clarify a little about this, if they consider this as a process or as a transfer mode, in which case I guess it should be state in the ASME IX as an accepted process.

Many thanks for yr answer.